A lane-keeping control device is known which controls a subject vehicle to travel along a target trajectory in an automated or autonomous manner (Japanese Patent Application No. JP2015-123929A, for example). When the traveling road width is wide, this device operates to set a lateral position feedback gain to a larger value than that when the traveling road width is narrow, thereby to perform natural and stable steering assistance in an expressway having a wide traveling road width. On the other hand, in a general road having a narrow traveling road width, optimum lane-keeping control is executed without interfering with the driver's avoidance maneuver.
In the above-described conventional lane-keeping control, however, the positional misalignment amount between the vehicle trajectory and the target trajectory at a forward gaze point is calculated to calculate a lateral position feedback control amount; therefore, on a road in which the variation in the curvature radius R is not monotonous, such as a general urban road that includes entry into an intersection and exit from an intersection, the current lateral position may take a shortcut or a detour with respect to the target trajectory, which may be problematic.